1. Field of the Invention
The present invention relates to a vehicular air conditioning apparatus mounted in a vehicle for blowing air into a vehicle compartment that has been adjusted in temperature by a cooling means or a heating means, for thereby adjusting temperature of the vehicle compartment.
2. Description of the Related Art
In a vehicular air conditioning apparatus that is mounted in a vehicle, internal and external air is introduced into a casing by a blower, and after cooled air, which has been cooled by an evaporator that forms a cooling means, and heated air, which has been heated by a heater core that forms a heating means, are mixed together in the casing at a predetermined mixing ratio, the mixed air is blown out from a defroster blow-out port, a face blow-out port, or a foot blow-out port, whereby adjustment of temperature and humidity in the vehicle compartment is carried out.
With this type of vehicular air conditioning apparatus, for example, it is known to provide a first blower for the purpose of introducing vehicle compartment air into the casing, and a second blower for the purpose of introducing external air outside of the vehicle compartment into the casing. In such a vehicular air conditioning apparatus, air that is introduced from an internal air introduction port by rotation of the first blower is heated by a first heat exchanger and then is blown into the vehicle compartment through a first air passage from the face blow-out port or the foot blow-out port. In addition, air that is introduced from an external air introduction port by rotation of the second blower is heated by a second heat exchanger and then is blown into the vehicle compartment through a second air passage from the defroster blow-out port. More specifically, a switching operation is performed such that when air is blown out from the face blow-out port or the foot blow-out port, the first blower is driven and air from the interior of the vehicle is introduced, whereas when air is blown out from the defroster blow-out port, the second blower is rotated and external air is introduced.
Further, using separate air conditioning devices having first and second blowers for introducing air, the first blower is arranged facing toward an external air introducing port of a duct, and the second blower is arranged facing toward an interior air introducing port. Additionally, the first blower includes a switching means, which is capable of switching the air that is introduced to the duct by the first blower between interior air and exterior air.
Moreover, the air that is introduced to the duct by the first blower is switched between interior air and exterior air by the switching means, and after the air has been adjusted in temperature by the heating means and the cooling means so as to provide a desired temperature together with the air introduced to the duct by the second blower, the air is blown into a desired region in the vehicle compartment through a face blow-out port, a foot blow-out port, or a defroster blow-out port (See, for example, Japanese Laid-Open Patent Publication No. 05-178068, Japanese Laid-Open Patent Publication No. 06-040236, and Japanese Laid-Open Patent Publication No. 06-191257).
Further, for example, in the vehicular air conditioning apparatus disclosed in Japanese Laid-Open Patent Publication No. 10-138737 and Japanese Laid-Open Patent Publication No. 2001-171329, an external air mode and an internal air mode can be selected by operating an internal/external air switching damper. However, when the external air mode is selected, since the air pressure applied to the front of the moving vehicle, i.e., ram pressure, becomes larger depending on the vehicle speed, when the vehicle is running at a high velocity, the amount of air that flows into the vehicle cabin increases, thus producing an effect on the temperature control capability of the vehicular air conditioning apparatus. For this reason, a butterfly type of ram pressure-adjustment damper is utilized as an internal/external air switching damper, and a control (hereinafter referred to as a “ram pressure control”) is performed, so that the amount of external air introduced to the vehicle compartment remains fixed, or changes no more than necessary.
Since the ram pressure increases corresponding to the vehicle velocity, for maintaining the intake amount of external air constant, it is required to make the opening area of the external air intake port smaller in response to the vehicle velocity. However, in the vehicular air conditioning apparatus disclosed in the aforementioned Japanese Laid-Open Patent Publication No. 06-191257 and Japanese Laid-Open Patent Publication No. 10-138737, when air is taken in from the exterior, since the air is introduced so as to face toward a flat surface of the ram pressure-adjustment damper, the flow rate of air is throttled by the ram pressure-adjustment damper while being drawn into the air conditioning apparatus. More specifically, a structure is provided in which external air is introduced from a substantially perpendicular direction with respect to the longitudinal direction of the ram pressure-adjustment: damper.
Owing thereto, the ram pressure-adjustment damper is blown upon and agitated by the ram pressure when the vehicle is running, and the opening of the ram pressure-adjustment damper is changed from a preset target opening, and thus cases occur in which errors are generated between the target opening and the actual opening. As a result, it is difficult for the introduction of external air to be adjusted properly by the ram pressure-adjustment damper and for external air to be introduced correctly into the air conditioning apparatus.
Further, when the ram pressure-adjustment damper is driven, for example, by an actuator, the ram pressure acts in resistance to driving of the ram pressure-adjustment damper, so that a comparatively large torque is needed. Thus, an actuator capable of generating such a large torque has been adopted, which tends to increase the size and scale of the actuator.